An electrochromic device (ECD) is a display device using electrochromic material that is colored or decolored by means of electrochemical oxidation and deoxidation according to an applying direction of electric current. The ECD keeps a transparent color if current is not applied thereto, but the ECD exhibits an inherent color according to the kind of electrochromic material if current is applied thereto. In addition, if the current direction is reversed, the color of the electrochromic material is decolored and thus restored into the transparent color. The ECD having such properties is widely used for mirrors and sunroofs of vehicle, smart windows and outside displays.
FIG. 1 schematically shows a basic configuration of an ECD. Referring to FIG. 1, the ECD 10 includes a first glass substrate 20 on which an upper electrode 30 made of transparent material and having an electrochromic material layer 40 is laminated, a second glass substrate 80 on which a lower electrode 70 made of transparent material and having an ion storage layer 60 is laminated such that the second glass substrate 80 faces the first glass substrate 20, and an electrolytic layer 50 injected between the electrochromic material layer 40 and the ion storage layer 60.
The ECD 10 configured as mentioned above is colored when a voltage is applied between the upper electrode 30 and the lower electrode 70 to flow current from the ion storage layer 60 to the electrochromic material layer 40. Also, the ECD 10 is decolored when a voltage opposite to the coloring case is applied thereto to flow current from the electrochromic material layer 40 to the ion storage layer 60.
Meanwhile, the ECD is classified into a memory type ECD that keeps a colored or decolored state once being colored and decolored though voltage is applied between the upper and lower electrodes, and a non-memory type ECD that keeps a colored or decolored state after being colored or decolored only when voltage is continuously applied between the upper and lower electrodes.
As mentioned above, the ECD has entirely different voltage applying patterns depending on its type, so driving devices for memory type ECD and non-memory type ECD should be separately developed and used, cumbersomely, in the past.